The Veterinary Resources Program, National Center for Research Resources, has established a Watanabe hereditable hyperlipidemic (WHHL) rabbit breeding colony as a resource for investigators. Watanabe et al. reported that there are two types of WHHL rabbits: type 1, those with premature coronary atherosclerosis; and type 2, those with slow development of coronary atherosclerosis. Both types of WHHL rabbits are characterized by high cholesterol and triglyceride concentrations. The two types of WHHL rabbits can be differentiated by their lipoprotein phenotypes. Agarose gel electrophoresis was used to determine the plasma lipoprotein electrophoretic patterns of 14 rabbits from the NCRR WHHL rabbit colony. The results showed that there are at least two lipoprotein phenotypes in the NCRR WHHL rabbit colony, and one is characterized by beta-VLDL. Findings by other investigators showed the properties of beta-VLDL isolated from WHHL rabbits are similar to those observed in humans with type III hyperlipidemia. The data suggest that there is a population of WHHL rabbits with both an apoprotein E and LDL receptor defect. Apoprotein E is being isolated from WHHL rabbit VLDL to determine if it is defective. Characterization of apoprotein E from NCRR WHHL rabbits may result in an animal model for type III hyperlipidemia. Identification of the two types of WHHL rabbits will be invaluable to the scientific community because it will eliminate the source of a possible confounding variable when WHHL rabbits are the laboratory animal model.